Formula: Ba4(Ti,Nb)8Si4O28Cl
Reflected/transmitted colour: colourless to yellowish brown
Pleochroism: strong, w = colourless, e = dark brownish to light greenish yellow
Optical isotropy/anisotropy: uniaxial
Optical sign: +
Refractive indices: w = 1.94, e = 2.16
Birefringence δ: 0.22
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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